Patients who have developed the acquired immunodeficiency syndrome (AIDS) have been infected with the human immunodeficiency virus (HIV) as transmitted by sexual contact or the exchange of blood or blood products. Patients infected with HIV vary in the rate of development of AIDS. Opioid addicts using shared needles make up a significant portion of the AIDS population. Various drugs that are abused are themselves immunomodulatory and immunocompromising, suggesting that in addition to the risks of multiple exposure due to needle-sharing, the cyclical effects induced by short acting opioids on the immune and bacterial defense systems may accelerate the process from viral exposure to the development of AIDS. The objective of this research, through the use of a simian model of AIDS (SAIDS), is to evaluate interactions between the chronic administration of opioids and the compromising of host defense systems during the development of AIDS. Since both AIDS and SAIDS are syndromes characterized by T4 lymphocyte depletion and immunosuppression followed by the acquisition of opportunistic infections, the progression of the viremia to involve an altered T4 function and loss of antibacterial host defenses (polymorphonuclear leukocytes and alveolar macrophages) will be monitored as well as general comportment and response to environmental disturbances. Monkeys will be trained to accept injections and to submit to sampling of body fluids. The animals will be hand fed, weighed daily, and observed for clinical symptoms of SAIDS. Blood samples will be drawn at appropriate intervals for evaluation of the progress of the viremia and changes in host defense mechanisms. Interaction between the viremia and opportunistic bacteremia will be characterized as a basis for judging modification induced by the induced opioid dependency.